double ropes

I've just been browsing old posts on half ropes. I just bought a new half rope to use in conjunction with a half rope that I've been using as a haul/rappell line for about a year (maybe a dozen times tops).
All of a sudden I'm worried! I had intended to use this system for alpine climbing this summer, in order to save weight--twice in the past I've been on the Diamond, climbing with partners' half ropes. They told me that usually you just clip both into the same biner, no problem, or for wandering pitches, you can alternate clip--they seemed to suggest that that was the exception.
So I've been intending to use these ropes not only for lower-angle wanderfests, but also for steep, straight, at my limit routes, e.g. Pervertical or D7--routes where I certainly might fall. But then I dredge up these old posts, where multiple people have said clipping both into the same piece of pro is very very bad! None of the company websites I checked mentioned this, nor did the fellow at Neptunes when I asked him for all the dirt. I can't see how anyone would ever climb near their limit on half ropes if this is true-- you are faced w/: 1) taking the fall on both ropes, clipped to the same pro or 2) taking a fall on a single 8.5 (how bad is that, anyone--especially if it's say a 30-50 footer?) or 3) clipping both to the same pro but with different biners (too much extra weight, and hard to do at your limit).
Can anyone explain exactly why it is so bad to clip both to the same piece (is it because of the fall factor, the ropes rubbing against each other, or what)? And exactly how bad is it? And just how bad is option #2 above?? Would there be any difference between clipping say the bomber #3 friend on Pervertical verses the perfect #4 stopper on the thin cracks of D7? I'm really worried that I've made a useless purchase here! I need reassurrance or resolution!

I was told that clipping both ropes to the same biner can cause rope burn during a fall and also that the impact force rating for the ropes is for each individual rope on its own. This means that if each rope is rated at 600 and you take a fall with both clipped to the same piece of pro, then the impact force is 1200, as opposed to a single rope with a 900 rating. This excess force may rip a questionable piece.

It appears that your mixing up half ropes and twins. With twins you clip both ropes into each piece of pro, with double rope technique, you alternate.

Doubles are thicker ropes, and falling on both ropes clipped into the same piece will generate more force than you want.

You could use either as a single for rapping or glacier travel, but each has distinct places in the mountains. Twins are great for things like pure ice climbs where there is not much chance of snagging on flakes and such. Half ropes are better in situations where you want a thicker rope, mixed or pure rock routes usually.

Cons: Two different skinny ropes = two different elongation factors = differential stretch and rubbing each other issues(I dont think this is the biggest issue unless you are planning on dogging with them or taking many multiple falls doubled up). This means that they will wear a little faster.

How much do you weigh? People talk about falling on single 8.8mm and I think it is quite possible, but I would do it more than a couple/three times unless you weigh 100lbs. 200lbs and falling on a single 8.8 means you will be stretching that bad boy to the moon. If you are pushing the 200lb mark falling on a pair of 8.8s I dont think is such a bad thing. If you are really worried about shock loading your gear(or yourself for that matter), use a screamer rather than relying on your rope/s solely for shock mitigation.

Pros: Light = right. Two ropes make a redundant system which is a plus(especially ice climbing). You dont need to take an extra cord for rapping. You can easily protect a zig-zagging route with little rope drag.

If all this talk concerns you over using two skinnys, then you can always go with a fatter cord and get a 7mm static line for a rap line/haul line back-up. It fits into a small pack easily with extra room and is very useful for speedier wall ascents and alpine rappels.

Me thinks you think too much. The functional difference between doubles and twins is that twins should always be clipped together. Doubles can be used either way. More often than not my two-rope program in the mountains (steep rock)is a 9 and a 10 in combination. That gives the option of having a true single rope if needed and the piece of mind of something less likely to cut. Besides, 9's don't have a very long life if used extensively on rock. I use double 9's on ice and easier rock or for long free climbs where I want to be able to climb longer pitches (55-60m). As for impact force, you'd have to take a big whipper and have the two ropes load at the exact same time for it to be anything near a concern. Impact force is by and large something for sport climbers to worry about. Don't worry, go climbing.

Please carefully study fall factors. The ratio of the length of fall divided by the amount of rope out.

eg; you are 10 feet past your last peice. You leader fall 20 feet but you are 80 feet up from the belay. The fall factor is low (1/4).Low stress on the rope.

2nd situation; you are 10 feet up from the belay and fall directly on to it (20 feet). The fall factor generated on the rope and belay of 2 is the most serious by far and stresses the ropes the most (the belay and the belayer as well).

Think of the rope(s) as a shock absorber. The longer the shock absorber relative to length of fall the better. The actual distance fallen is less important than the ratio. (fall factor.

note; none of these factors come in to play if the leader hits a ledge or the ground before the rope has a chance to come in to play.(no kidding genious).

What does this imply:

1. To reduce a fall factor of 2 (a fall directly on to the belay) you can give the leader more slack provided that this does not cause him/her to hit anything on the way down including the ground and that the belay is bomb proof and assuming the leader can still climb when they bend their brain around the concept that they are safer taking a longer fall in some situations. eg; you are 10 feet past the belay and the belayer has given you 10 extra feet of slack. you take a leader fall of 30 feet but on to 20 feet of rope. The factor generated is 1.5 (30/20) which is considerably safer for the rope than a 2.

2; from the ropes point of view, a 10 foot fall can easily generate more stress in certain situations that even a 60 footer or more can in others.

3; That first peice off the belay is so critical in preventing a fall factor of 2 that if possible, reach up and place your first peice while still standing on the belay.( I always have 1 shock absorber sling for this first placement).

So what does this have to do with Twin ropes (half ropes). Neither of the individual ropes in a twin (1/2) is rated to accept a fall factor of 2. As the name implies, these ropes were designed to be used as twins (together or as each 1/2 making a whole rope system where a fall factor of 2 may occur. Check with the rope manufacturer as to the fall factor rating.

This vs a Double rope system which means that you have 2 fully competent individual ropes in your system. In a twin system, to address the potential of a fall factor of 2, you need both ropes clipped in at the same time at least untill you have your first couple of peices in at which time the fall factor will have been sufficiently reduced and you can revert to individually clipping each rope. (double rope technique).